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# NEET Physics  Magnetism  Practice Q & A

1. The coercivity of a small magnet where the ferromagnet gets demagnetized is 3 × 103 A m–1. The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetized when inside the solenoid, is :

 60 mA 3 A 6 A 30 mA

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2. Hysteresis loops for two magnetic materials A and B are given below:
magnetic materials.png" alt="Hysteresis loops for two magnetic materials" style="margin:0 auto;" />
These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use:

 A for electromagnets and B for electric generators A for transformers and B for electric generators B for electromagnets and transformers A for electric generators and transformers

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3. The magnetic lines of force inside a bar magnet

 are from north–pole to south–pole of the magnet. do not exist. depend upon the area of cross–section of the bar magnet. are from south–pole to north–pole of the magnet.

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4. An iron rod is placed parallel to magnetic field of intensity 2000 A/m. The magnetic flux through the rod is 6 × 10–4 Wb and its cross–sectional area is 3 cm2. The magnetic permeability of the rod in Wb/A–m is

 10–1 10–2 10–3 10–4

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5. The magnetic susceptibility is negative for

 Ferromagnetic material only Paramagnetic and ferromagnetic materials Diamagnetic material only Paramagnetic material only

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6. A particle of charge –16 × 10–18 coulomb moving with velocity 10 ms–1 along the x–axis enters a region where a magnetic field of induction B is along the y–axis, and an electric field of magnitude 104 V/ m is along the negative z–axis. If the charged particle continues moving along the x–axis, the magnitude of B is

 10–3 Wb/m2 103 Wb/m2 105 Wb/m2 1016 Wb/m2

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7. A magnetic needle is kept in a non–uniform magnetic field. It experiences

 a torque but not a force neither a force nor a torque a force and a torque a force but not a torque

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8. At certain place, the horizontal component of earth’s magnetic field is 3.0 G and the angle dip at the place is 30°. The magnetic field of earth at that location

 4.5 G 5.1 G 3.5 G 6.0 G

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9. Curie temperature is the temperature above which

 a ferromagnetic material becomes paramagnetic. a paramagnetic material becomes diamagnetic. a ferromagnetic material becomes diamagnetic. a paramagnetic material becomes ferromagnetic.

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10. electromagnets are made of soft iron because soft iron has

 high susceptibility and low retentivity low susceptibility and high retentivity low susceptibility and low retentivity high susceptibility and high retentivity

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